U3 Chapter 17: Gene Expression From Gene to Protein

Question 1

Gene Expression

Answer 1

The information encoded in genes is used to make specific polypeptide chains (enzymes and other proteins) or RNA molecules

Question 2

Transcription

Answer 2

The synthesis of RNA complementary to a template strand of DNA
- 3 stages: initiation, elongation, and termination
- promoter sequence, establishes where RNA synthesis is initiated often including a TATA box (a DNA sequence that indicates where a genetic sequence can be read and decoded) in eukaryotes

Question 3

Translation

Answer 3

The synthesis of a polypeptide whose amino acid sequence is specified by the nucleotide sequence in messenger RNA (mRNA)

Question 4

Codon

Answer 4

Genetic information is encoded as a sequence of nonoverlapping nucleotide triplets
- either translated into an amino acid [61 of the 64 codons] or serves as a stop signal [3 codons]
- codons must be read in the correct reading frame

Question 5

RNA Polymerase

Answer 5

Links together RNA nucleotides complementary to a DNA template strand

Question 6

Transcription Factors

Answer 6

Help eukaryotic RNA polymerase recognize promoter sequences, forming a transcription initiation complex

Question 7

RNA Processing (eukaryotic mRNA)

Answer 7

Includes RNA Splicing, the addition of a modified nucleotide 5’ cap to the 5’ end and the addition of a poly-A tail to the 3’ end

Question 8

Intron

Answer 8

The sequence of DNA in between exons that is initially copied into RNA but is cut out of the final RNA transcript and therefore does not change the amino acid code

Question 9

Exon

Answer 9

The sequence of DNA present in mature messenger RNA, some of which encodes the amino acids of a protein. Most genes have multiple exons with introns between them

Question 10

RNA Splicing

Answer 10

Introns are removed and exons joined

Question 11

Spliceosomes

Answer 11

A ribonucleoprotein complex that is the site in the cell nucleus where introns are excised from precursor messenger RNA and exons are joined together to form functional messenger RNA
- ribozymes (some RNA) act like catalysts
- presence of introns allows for alternative RNA splicing

Question 12

Transfer RNA (tRNAs)

Answer 12

A small RNA molecule that plays a key role in protein synthesis. Transfer RNA serves as a link (or adaptor) between the messenger RNA (mRNA) molecule and the growing chain of amino acids that make up a protein

Question 13

Aminoacytl-tRNA Synthetase

Answer 13

A tRNA lines up via its anticodon at the complementary codon on mRNA

Question 14

Ribosome

Answer 14

Made up of ribosomal RNAs (rRNAs) and proteins, facilitates this coupling with bonding sites for mRNA and tRNA
- the formation of peptide bonds between amino acids is catalyzed by rRNAs as tRNAs move through the A and P sites and exit through the E site

Question 15

Signal Peptide

Answer 15

Targeting and membrane insertion of secretory and membrane proteins in both prokaryotes and eukaryotes

Question 16

Polyribosome

Answer 16

A cluster of ribosomes linked together by a molecule of messenger RNA and forming the site of protein synthesis

Question 17

Point-Mutations

Answer 17

Changes in one DNA nucleotide pair which may lead to production of nonfunctional proteins
- small scale mutation
- nucleotide pair substitutions can cause misuse or nonsense mutations
- nucleotide pair insertions or deletions may produce frameshift mutations

Question 18

Mutagens

Answer 18

Chemical or Physical can cause DNA damage that can alter genes